1. Field of the Invention
The present invention relates to a flange fastening structure.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2008-232039 discloses a technique in which, in an internal-combustion engine, a flange of an intake manifold is fastened with a bolt to a mounting surface of a cylinder head, with a plastic housing for a tumble control valve interposed therebetween. In this technique, a metal collar is embedded in the housing, and an annular raised base is formed on an end face of the housing that is in contact with the flange of the intake manifold. The raised base is formed such that it faces the periphery of the collar. The bolt passes through the flange and the collar and is screwed into the mounting surface of the cylinder head. While the raised base is being compressed by a fastening force of the bolt, the intake manifold and the housing are fastened together to the cylinder head.
Japanese Patent No. 4065270 discloses a technique in which, in an internal-combustion engine, a mating surface of a flange of a plastic intake manifold is fastened with bolts to an end face of a metal throttle body. In this technique, nuts are held in respective recessed portions formed in the flange of the intake manifold. Additionally, collars are embedded between the mating surface of the flange and the nuts. Then, the bolts inserted from the side of the throttle body are passed through the respective collars and screwed into the respective nuts.